Do I have any gaps that anyone sees based on what I have so far? I'd like to have the most versatility in my bag. Should I be considering adding a lens or switching one out?

I'll give a bit of background in terms of my photography usage: I've been shooting for about a year now. My goal of photography is to document my life with my family for the most part, and turn this into more of a "serious hobby" than just the token family member with the nice camera. whether that be portraits during family events or scenic portraits from our family vacations I just want to have versatility in my bag.

My husband and I have our first child on the way in March (which I'm excited to shoot my newest subject!) and I'll generally be using camera for that purpose, at least for foreseeable future. Right now I've been primarily shooting family portraits and photographing our yellow lab, given that I'll be a stay-at-home mom soon I may find that I'll have more time to vary my photography - which I welcome because I also want to get more accustomed to shooting sports/action photos. My husband and I are both avid golfers and like going to sporting events so having the ability to get action shots when necessary would be nice too. We are headed to Hawaii in a few weeks for a "babymoon" so if there's any advice on lenses to take too that would be appreciated! Debating whether or not to bring my entire camera bag and give up my other carry-on

Given this info - any advice on my current tool belt would be greatly appreciated, whether that be upgrades, adding or deleting lenses. I'm pretty well set for now on my D5100 as body, really have liked what it produces.

You have the focal ranges covered, and there is very little else that you need.

I have some suggestions, but they are all "desirable" rather than essential. The best test is when you feel that you can't do something with your kit that you need to do.

You have the 50 1.8 (an excellent lens) and good for portraits on DX. Have you considered the 35/1.8 - not such a restricted angle of view, and a bit moe versatile for baby shots etc. The only drawback is that the focal length is not hugely different from the 50.

I like wide angle, and often find myself going wider that the 18. You could consider substituting a 16-85 for the 18-55 or getting a wider zoom (Sigma, Tamron have some very wide zooms). This means spending some money and you would need to trade off benefits against costs.

I wouldn't have thought of flash until Old Carlos mentioned it, but it is certainly worth considering. Bounce is a good idea (and would be excellent for babies). I have an SB400 - very small, resonably powerful, and controlled entirely from the camera - some deride this unit, but it is low profile, has bounce settings, is secure on the camera and has reasonable power in a domestic setting. The other suggestions from Old Carlos are good too.

for your holidays id have said you want a nice wide lens to get some really wide scenic landscapessomething like a Sigma 10-20mm f4-5.6 EX DC HSM, this has its own focus motor so would work on the 5100